MIAMI — Amanda Paradiz is 16 weeks pregnant, and she has a mission: to get through her entire pregnancy without a single mosquito bite.

It hasn’t been easy. Ever since health officials in July announced four cases of Zika transmission by local mosquitoes detected in a Miami-area neighborhood, Mrs. Paradiz and her husband Alex have largely secluded themselves in their Broward County home. They canceled a vacation, and stopped taking evening strolls around the lake and swimming in the neighborhood pool. To walk the dog, Mrs. Paradiz, 35, throws on long pants and a hoodie, even though it’s 90 degrees outside. She’s debating quitting her job as a sales rep, to avoid coming into contact with a mosquito that might carry the Zika virus, which can lead to devastating birth defects, including an abnormally small head, called microcephaly.

“All it takes is one mosquito bite to change the entire course of our lives,” Ms. Paradiz said.

In the past three weeks, the number of confirmed Zika infections in the greater Miami area has increased to 35, including 25 linked to the one-square-mile neighborhood of Wynwood considered the Zika zone, as well as isolated cases outside Miami-Dade County in Broward and Palm Beach counties. Since Thursday, the number has included a small cluster in Miami Beach, suggesting that there is at least one other location where mosquitoes may be transmitting the virus locally. Federal health officials now are considering whether to advise pregnant women to avoid traveling to the area.

Public health officials have emphasized they do not expect the virus to spread here as it has in other countries because many homes have screened windows and air-conditioning, which keeps mosquitoes at bay. But pregnant women still are worried.

Some expectant mothers are choosing confinement indoors to avoid mosquitoes. Women who wouldn’t dream of drinking coffee while pregnant now are coating exposed limbs in bug spray, a tactic recommended by health officials. Some women even are considering temporary moves, leaving their homes, families and doctors to stay with relatives or friends far away from a Zika zone until they give birth.

“Patients are very anxious, and they bring up the subject of Zika with me before I even get a chance,” said Dr. Elizabeth Etkin-Kramer, an obstetrician-gynecologist who is a past president of the Dade County Medical Association. “Before, this was an ocean away. Now it’s in their backyard.”

While the Zika epidemic has been sweeping across Latin and South America and the Caribbean since last year, in the United States it is still relatively new. So far, some 2,260 infections have been confirmed, including 529 pregnant women, according to the Centers for Disease Control and Prevention.

But those cases involved people who are believed to have been infected while traveling, as well as 22 who contracted it by having sex with an infected person. Now that the virus has been transmitted through local mosquitoes, pregnant women say they feel vulnerable and frightened, and wonder how they can keep mosquitoes at bay during an entire pregnancy while living in a state that is swarming with the insects.

At a regional meeting of obstetricians and gynecologists in Orlando last week, Zika was the main topic of conversation, said Dr. Karen Harris, an obstetrician-gynecologist in Gainesville who heads the Florida arm of the American Congress of Obstetricians and Gynecologists.

“It’s hard on the patients, but it’s also hard on the staff, because we don’t have anything to offer but prevention,” she said. “We can’t answer their questions. If you get Zika a month before you’re due, does that affect the baby? We don’t know. There’s total uncertainty.”

The large black-and-white mosquito that carries the Zika virus, named Aedes aegypti, doesn’t normally fly more than about 500 feet in its lifetime. Health officials assume that Miami-area mosquitoes picked up the infection from someone who had just returned from Latin America or the Caribbean with the virus in his or her blood.

The latest guidelines direct obstetricians to assess every pregnant patient for exposure to Zika at each prenatal visit, and counsel them to use condoms and insect repellent to lower their risk for exposure.

Dr. Aaron Elkin, a Broward County obstetrician-gynecologist who treats a diverse group of patients from Miami and surrounding areas, keeps a basket of free condoms on the counter in the reception area, along with containers of Off bug spray. Dr. Elkin spent every visit last week discussing Zika precautions, assuring women that bug spray would not harm the fetus, taking blood and urine samples for tests and doing ultrasounds.

“Every pregnant woman who comes in for prenatal care wants Zika testing,” Dr. Elkin said. “You can’t say no to them. They’re very frightened. I’m doing 15 tests a day.”

One patient, Idit Zalouf, a 37-year-old who lives in Sunny Isles Beach just north of Miami Beach, is five months pregnant. She showed Dr. Elkin a bracelet she bought that she thinks will protect her from mosquitoes. Dr. Elkin advised her to use insect repellent with DEET.

“Do you think it would be good for me to go to New York for a while?” she asked him. “If a pregnant woman gets the Zika, what does she do?”

Dr. Elkin tried reassuring her that preventing mosquito bites and other forms of Zika transmission should be her focus, and that it would be difficult to manage her care from afar.

Later Ms. Zalouf said she may move anyway. “I think it’s better to be away from here,” said Ms. Zalouf. “I’m stressed about it. It’s very frightening. “

Another patient, Unique Robinson, a 22-year-old licensed practical nurse who is not working now and lives in Broward County, said she is terrified. She rarely ventures outside her home, except to go to the mall or the movies.

“I’ve looked it up and seen the babies, how they come out. I don’t think I could handle that,” she said, her voice breaking. She often goes online to look up information. “The internet makes it worse.”

Some patients are worried about Zika, but find it difficult to take precautions. Malorie Fitzgerald, a 29-year-old part-time secretary who is 33 weeks pregnant with her third child, has separated from the father and has been living in a homeless shelter in an area of Miami adjacent to Wynwood. While most patients came to the office wearing long pants and long sleeves, Mrs. Fitzgerald, who caught a bus, was wearing an ankle-length dress with a halter top.

At the shelter she shares a room with 25 people, and they are lax about leaving doors open. She hangs blankets around her bunk bed to keep flies and mosquitoes out, to no avail. “I get bit a couple of times a day,” she said. “It’s a little less since the doctor gave me a can of Off. But the mosquitoes and flies are horrible there.”

Dr. Elkin runs an ultrasound, and reassures Ms. Fitzgerald that the measurements are normal. It’s not a perfect guarantee, however. Infections can occur at later stages of pregnancy, and the scan won’t pick up more subtle abnormalities caused by Zika that are not visible, like stiff joints and eye damage.

“That is the head of the baby, see? It’s completely normal,” Dr. Elkin said. Ms. Fitzgerald smiled with relief. But he repeated his advice about prevention. “Wear long clothes and use the Off!”

But even the most vigilant efforts to prevent mosquito bites are not always successful. Lori Tabachnikoff, 36, who is 24 weeks pregnant with her first child and lives in South Miami, said she was fortunate because her employer, the Greater Miami Jewish Federation, located just outside Wynwood, has allowed her to work from home to minimize her time outdoors.

Even so, mosquitoes sneak in. She recently let a plumber into her home and was soon bitten by a mosquito that must have slipped in at the same time. She has been bitten five times so far this summer, and she and her husband recently went to the health department at 4 a.m. to get in line to be tested. There were already four couples ahead of them. They are waiting for the results.